JavaSpring的再理解_1

 

Spring再学习

spring的原理

主要包括两个部分，其中AOP和IOC

• AOP主要是面向切面编程
• IOC主要是容器的概念
  下面我从下面的两个方面对Spring进行学习，以便于后续找工作具有一定的谈资

pojo实体类

public class Category {
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    private int id;
    private String name;
}

这里是实体类，主要有几个相关的属性和方法信息，这里需要注意的是get和Set的方法

在src目录下，新建applicationContext.xml文件

applicationContext.xml是Spring的核心配置文件，通过关键字c即可获取Category对象，该对象获取的时候，即被注入了字符串"category 1“到name属性中

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
   http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/aop
   http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
   http://www.springframework.org/schema/tx
   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
   http://www.springframework.org/schema/context     
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">
  
    <bean name="c" class="com.how2java.pojo.Category">
        <property name="name" value="category 1" />
    </bean>
  
</beans>

这里通过class获取实体类，并且将实体的信息注入进去，并且命名为C

测试注入的信息

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
 
import com.how2java.pojo.Category;
 
public class TestSpring {
 
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext(
                new String[] { "applicationContext.xml" });
 //注意再这里对其进行实体化，然后对对象采用getBean的方法获得对象的
        Category c = (Category) context.getBean("c");
         //这里对对象的方法进行输出，最终得到相关的名称的信息
        System.out.println(c.getName());
    }
}

原理图

• 传统的方式采用new的方式实现一个对象 int a = new int();
• 对于Spring的方式来说，主要将创建对象的方法与步骤交给Spring来进行操作，得到最终的结果。 int a = spring a；

Product.java的类方法信息

Product类中有对Category对象的setter getter

public class Product {
 
    private int id;
    private String name;
    private Category category;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Category getCategory() {
        return category;
    }
    public void setCategory(Category category) {
        this.category = category;
    }
}

applicationContext.xml

 

<bean name="c" class="com.how2java.pojo.Category">
    <property name="name" value="category 1" />
</bean>
<bean name="p" class="com.how2java.pojo.Product">
    <property name="name" value="product1" />
    <property name="category" ref="c" />
</bean>

TestSpring

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
 
 
public class TestSpring {
 
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext(new String[] { "applicationContext.xml" });
 
        Product p = (Product) context.getBean("p");
 
        System.out.println(p.getName());
        System.out.println(p.getCategory().getName());
    }

修改applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
   http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/aop
   http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
   http://www.springframework.org/schema/tx
   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
   http://www.springframework.org/schema/context     
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">
  
    <context:annotation-config/>
    <bean name="c" class="com.how2java.pojo.Category">
        <property name="name" value="category 1" />
    </bean>
    <bean name="p" class="com.how2java.pojo.Product">
        <property name="name" value="product1" />
<!--         <property name="category" ref="c" /> -->
    </bean>
  
</beans>

@Autowired

在Product.java的category属性前加上@Autowired注解
@Autowired
private Category category;

import org.springframework.beans.factory.annotation.Autowired;
 
public class Product {
 
    private int id;
    private String name;
    @Autowired
    private Category category;
 
    public int getId() {
        return id;
    }
 
    public void setId(int id) {
        this.id = id;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public Category getCategory() {
        return category;
    }
 
    public void setCategory(Category category) {
        this.category = category;
    }
}

@Resource

这里采用这个这个注解和@Autowired的情况一样
@Autowired
public void setCategory(Category category)

import javax.annotation.Resource;
 
public class Product {
 
    private int id;
    private String name;
    @Resource(name="c")  //这里是将这个属性进行命名的操作，
    private Category category;
 
    public int getId() {
        return id;
    }
 
    public void setId(int id) {
        this.id = id;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public Category getCategory() {
        return category;
    }
     
    public void setCategory(Category category) {
        this.category = category;
    }
}

Bean注解的学习

这里教程上在application的启动配置上面修改了一些内容
修改applicationContext.xml，什么都去掉，只新增：<context:component-scan base-package="com.how2java.pojo"/> 那么这一部分就代表了扫描某一个类的情况信息。
其作用是告诉Spring，bean都放在com.how2java.pojo这个包下

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
    xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
   http://www.springframework.org/schema/beans
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/aop
   http://www.springframework.org/schema/aop/spring-aop-3.0.xsd
   http://www.springframework.org/schema/tx
   http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
   http://www.springframework.org/schema/context     
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">
  
    <context:component-scan base-package="com.how2java.pojo"/>
     
</beans>

那杨这里就代表了相应的数据信息内容

@Component

product的类的方法,这里在类的方法上面

import javax.annotation.Resource;
 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
 
@Component("p")
public class Product {
 
    private int id;
    private String name="product 1";
     
    @Autowired
    private Category category;
 
    public int getId() {
        return id;
    }
 
    public void setId(int id) {
        this.id = id;
    }
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public Category getCategory() {
        return category;
    }
     
    public void setCategory(Category category) {
        this.category = category;
    }
}